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This is Hacker Public Radio episode 3,911 from Monday 31 July 2023.

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Today's show is entitled, an overview of the Act Command.

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It is part of the series Lightweight Apps.

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It is the 150th show of Dave Morris, and is about 21 minutes long.

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It carries an explicit flag.

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The summary is a Pearl-based Grap-like tool that can search by file time.

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Hello everyone, welcome to Hacker Public Radio.

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My name is Dave Morris, and I'm talking today about a command, which I have put into the

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category or the series of Lightweight Apps.

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So what this is, is a Pearl-based tool that behaves like Grap.

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It actually uses the name Beyond Grap on the website, which I refer to in the notes.

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So this tool is called ACK, quite sure why, but it's a good thing.

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And it's got three main features that I use.

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I don't use it a huge lot.

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It's not a thing I use for every search of a file, but it's great for certain things.

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First of all, it can restrict the searches to files of a particular type.

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So there's a way of classifying files in terms of type, which I'll talk about in a minute,

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and it will search only those.

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The regular expressions that it uses, I mean, Grap will handle, plain text, stuff,

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and regular expressions of various sorts, including a Pearl-1.

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But this one is only Pearl that it uses.

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I think it's actually possible to simplify it, but the default is Pearl anyway.

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And Pearl, of course, has one of the most powerful feature-rich types of regular expressions.

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So that's to me, that's fantastic.

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And it's got features like you can limit the search area within a file if you want to.

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I'm not going to go into that.

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There's a lot to say here if I was to dig deeply into all aspects of this command,

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and I'm not going to do it because I don't want to.

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Well, you to death, it's almost a series in itself if I were to go into that level of detail.

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It's fantastic, I believe, but it's a little complex to use,

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and I use it mainly in special cases where I need the features I've just mentioned.

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So I'll just give you a flavor of what it can do and leave you to research it more if it sounds interesting.

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So you can install it in the usual sorts of ways.

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I actually installed it as a package with it.

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I used Debian, so I used App to do it, App to install.

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So do App to install, App can, that's fine.

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I only, as I was preparing the show, I noticed that I was using version 3.6.0.

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And that's a little bit behind, and there's a new version 3.7.0,

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which you can get details about from the website.

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It suggests that you might want to install it as a Pearl module using C-Pan,

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but if you're not a Pearl user, these are things you might not want to take on board.

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Let's just talk briefly about Pearl regular expressions,

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as I said, they're very sophisticated and have grown tremendously over years.

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I think Pearl was grand breaker in terms of regular expressions,

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because a lot of other regular expression engines follow Pearl's lead.

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It's certainly the power of our use, Pearl of quite a long time now,

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and the power of it is quite spectacular.

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What happened during the last number of years was that there came to be a thing called

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the Pearl compatible regular expressions library.

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This was put together by a guy called Philip Hazelor from Cambridge University.

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He did this in 1997. I was particularly interested in this,

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because I was working at RAN XM, the male transfer agent,

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and PCR-E, Pearl of a regular expressions, were implemented within it,

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and Philip Hazel was the author of XM.

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So he did this, and PCR-E is available in quite a lot of other areas.

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I think at one point Python used it, I'm not sure it does now, but anyway.

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But since the original PCR-E, there's come a version called PCR-E2,

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so he's still developing it, and it is very widely used.

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The act documentation refers you to various Pearl manuals for detail to use

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the regular expression syntax in detail, although you can use it in a simplistic way,

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which is what I do mostly. I don't use the full power of it, but it is quite nice

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to be able to get into some of the Pearl stuff.

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But there's plenty of documentation if you're interested.

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In fact, Gnu-Grap, which would be the one that most people will have on a Linux system,

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it can use Pearl compatible regular expressions when doing it's matching,

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but I can't remember what the option is. Mine is a cabrical piece,

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not sure, but if you look at the documentation for Gnu-Grap, it says this is experimental.

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I've not really gotten to using that in a big way.

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So let's talk about the file type, as you mentioned before.

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So this act command has got rules for recognizing file types,

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and it does this by looking at the name extensions,

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fairly obviously, so dot HTML or dot py.

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It can also look at the file's contents to see the sort of first line,

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which has got, what do they call that? Some sort of magic thingy.

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That's you determine what a file is called. I completely forgot the terminology.

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You can find out what Act knows about in terms of types by giving it the option

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hifin-hifin help hifin types, or you can use Act based hifin-hifin dump.

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Some of the examples are CC, as a type, and those are C files,

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Haskell, Haskell files, Lua, Lua files, Python for Python files,

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Shell for Bash and other Shell command files.

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And these names can be used with the options,

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Lua case hifin-hifin-hifin-hifin-hifin type equals the type name,

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and also by preceding the type name with two dashes, if you wish.

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I think that might be the particular way of doing it might not be available in the future,

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because it says it's deprecates it somewhere. That's what I use.

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You can also say files not of this type by using hifin-hifin-hifin-hifin type equals no

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followed by the type string. Anyway, now I use that much of a sub. I don't usually want to look

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at files which are not Shell script, because I'll be everywhere the else and I don't want it.

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But it's good that you have it. So we've got a little example here to check files in the current

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directory, which are Shell scripts, then you might want to do this with the command

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AC as base. Hifin-hifin-shel, space, and then the search string, which in my case is declare.

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And I'm actually in the directory where I prepare my, it's better shows, and it finds

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one in title bash snippet using co-proc with their skew light. It finds a shell script there

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and shows me online 11. There is the occurrence of the word declare. And it's quite nice that

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it by default gives you the line number. It also does coloring of these things when you search

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all of which you can turn off and mess around with to enormous degrees. You can add your own

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file types to hack and there's a configuration file called .acrcacrc, which you can add more types

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to and talk about that next. So that configuration file .acrc, and it contains, as the manual says,

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command line options that are pre-pended to the command line before processing. So it's useful

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way to add new types or modify existing ones. There are a number of places that can be placed

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and the documentation will tell you that. But I put mine in my home directory where I keep all my

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other configuration files. It can be another other more regular places in the Comfort directory

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You can actually create a new .acrc with the option hif and hif and create hif and a ckrc.

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So it will write out an example series of settings on sanded out and you can just pipe it to

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the file. That's all the defaults that have built into the script, but it means that you've

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got them somewhere where you can change them if you wish. Now I have a lot of marked down files

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in my directory where I do all my hbr talks. I write everything in marked down. And for some

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reason I'm not sure why I did this originally gave them the extension of .mkd. I must have seen

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somebody else do that or just seemed like the right thing and I wasn't sure what was better. But

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act recognises .md and .markdown as signaling marked down file. So I wanted to add .mkd to the list.

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And it was pretty simple to do. There's two commands you can use within your

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accuracy. There's one which is dash dash type dash add equals marked down .call on .ext

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call on .mkd. So it depends the particular extension to the existing list or you can you can use

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dash dash type dash set equals marked down .call on .ext .call on .md .call .mkd .call

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marked down. Well that does is to replace the existing settings. That's why it uses set as

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supposed to add after type. And you just give it the list. It currently existing list plus

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whatever else you've added to it. You can put comments in the file too. So if you then dump the

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settings. So in done this you can see that marked down is listed with .md .markdown and .mkd

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as detectable extensions. So if I do a search for marked down in the directory I'm in where my

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various HPR shows live. I keep them all around forever .ackspace-dashmarkdown

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space then in quotes in a well-in-law case space ear. I get back one match, one file match and then I

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get a bunch of lines that contain the string in it ear. Now there are a lot of options to act

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the general usage pattern for using the command is that you type act followed by list of options

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followed by a pattern which is the thing you're matching usually in in files but but come on to that

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more in a moment and followed by an optional list of files or directories. If you don't give

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a list of files or directories then it will look at the current directory and will recurst

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down into subdirectories and the pattern that I mentioned is the PCRE search string which is usually

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enclosed in single quotes for so it doesn't get interpreted by the shell. There are some

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cases where you don't use a pattern but look at that briefly in a moment. They can look at the full

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documentation for the usual man act command and the alternative to doing that is to use

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act itself to report it's man page which is act space-dashman. There is also an option

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dash-dash help which gives a summary of all the available options which is actually find

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more useful because it's usually options I'm trying to remember and it's to scan through

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rather the full documentation. There's got a few options to refer to here. There's quite a lot

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that are specific to act and some of the sentences meant to be a prep standing there are some

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which are common to prep but I won't look at too many. Well the first one is one that you do find

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in prep which is dash-i and that makes the the pattern matching case incentive. It's possible to

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do that within the pearl expression. You can say I want these only to be matched with. I don't care

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about the case when matching but it's a lot easier to use it as an option I find. Then we get to

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dash-f which is about searching for files by name so it only prints the files that would be

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searched. It comes back with the list of file names. It doesn't do any searching but it's useful

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for finding things within a directory which are a particular type or match a pattern or whatever.

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dash-g is the same as dash-f but in this case you use a pattern and you look for files which match

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that pattern whose names match the pattern like the contents. But it that overlaps what you get

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with the type business so it's useful in some cases but can be a little bit misleading. Then we get

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dash-l which reports the file names which contain matches for a given pattern. So it's not actually

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showing you the matches but you're showing you the file which would match and the dash capital

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hell reports file names which do not match the pattern. Then you've got dash-c which you'll

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get in-grap which reports file names and the numbers of matches when you use it. So it actually

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reports all files that match whatever it is you're matching against in terms of file types or names.

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It reports them all and it gives you a count of zero if there are no matches which I find bit

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bit of pain not that useful but if you use it with hyphen L then you only see the names of

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files that have matches and a count of the matches. So I've just used it yesterday looking through

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a bunch of files to see if any of them had a particular string in them because I needed to

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edit it because it was a grammar grammatical error and so using the hyphen C and I from L was

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a great way to do it and then we have dash-w which forces the search pattern to match only

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whole words. So a lot of times there isn't a way of doing that in-grap that I know of.

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I think you're wrong actually. I think some of the the regular expression capabilities of

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Grap will allow you to do that anyway but it's sometimes useful to be able to say look that's

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sequence of characters I've just given you that I want you to look for is the word or our words

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as opposed to just being an ABC anywhere in any any text. So there's a lot. There's actually a lot

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of power in this possibly too much. I don't use it all by any means. I've got a few examples.

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The first example is looking for all mark-down files in a directory. So first option was to use the

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dash f option. So I typed ack space dash dash mark-down space dash f space and then the

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name of a sub-directory nightcore tube torch. So sure I did some time ago and it comes back with the list

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of names which are the mark-down files within the within that directory or mkd files.

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Now there are many other ways you could do that. You could use the find command to find them.

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That's that would have been what I would have used in the past but I find ack just as a nice

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job. But given alternative here using the dash g option so ack space dash g and then we're using

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a pattern. The pattern is open-quote backslash dot which matches an actual dot mkd dollar

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closed quote or that are saying any file name you get back which ends with dot mkd and then the

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name of directory nightcore tube torch and it comes like the same file names achieved by a different

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method. I think I would use the former in pretty much all cases but if you don't have a type that you

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can use to do the search then the g thing is an alternative. So what about finding the names of files,

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listing the names of files that contain a match with some string and the number of matches per file.

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So this one is the act command followed by dash dash mark done to look into markdown files again.

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This time I'm using dash LCI so I've can catonated three of the options together which you can do

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with single character options and by the way these options are usually I think in all cases have

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no not all cases but many cases have a single character version and a double hyphen followed by a

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long version so but I'm using the short versions here for demonstration purposes so LCI means

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use the options dash L dash C and dash I. Now my match string my pattern is

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open quote, bxb ea rxb now that's using one of the pearl regular expression capabilities which is

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to denote a boundary and this case a word boundary. So the the bxb is can be an opening

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boundary or closing one. So it's saying look for the word ea ea r which is a word a

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standalone word. Now there are other ways of doing that you can do something like that in grep

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but the regular expression syntax is very in the way that this word boundary thing is done and

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gets a little bit messy but the point is that it's separating out the sequence ea r from

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for example in the word pearl as an ea r but you don't want pearl to be returned because it's not

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a word I mean it's a word but I mean it doesn't got the word ea ea in it so example three

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just looking forward in a simpler way similar to example two where we used the bxb boundaries

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you can achieve this alternatively by making the pattern simpler just the word ea r ea and

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preceding it with dash w which as I mentioned before says treat this as a word or words I think but

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I might have experiment with that but in both of these cases what you get back is list of

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file names and each file name is followed by colon and a number which tells you how many matches

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for that word exist in the file. There's the same in both cases of course in example two and three

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so I thought about stop with the examples here because it's getting a bit too far a bit too long

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otherwise so that's it then there's some references to the pearl reference manuals and tutorials

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and stuff and the the site where ack can be found and details about it so a little bit of that

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that's the end and I hope you found that useful okay then bye

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and our synced of net on this otherwise stages they show is released on their creative

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